Please note that we do not recommend to make manual changes to the database since this may harm your project.
The supported way to delete comments is through the Sitefinity backend under Content -> Comments
or delete the comments using the API. You may refer to the following samples from our documentations for more details:
Delete comments (6.1 and below)
This way the comments will be deleted properly from the database and there will be no orphan records remaining.
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Sitefinity CMS Ideas&Feedback Portal
and vote to affect the priority of the items